We determined from behavioral and ecological observations that there are two subspecies in Schizotetranychus miscanthi Saito which distributes in Japan. Next, we examined morphological characters of two spider mites species, in order to determine characters reflecting mite body size regardless of mounting methods. Several body characteristics of flattened and non-flattened specimens of Schizotetranychus longus Saito and S.miscanthi Saito were investigated. There are several characters which are not influenced by mounting conditions regardless of sex and species, and which reflect well body length and width.We conducted studies on the phylogeny of Teteranychini by the use of traditional morphological and DNA based methods. The analyses of DNA variation mainly on the genus, Schizotetranychus suggested that there is a consistency between genera categorized by morphological observations and those detected by DNA based method. However, there appears to be a discrepancy between the phylogenic tree expected from morphological data and that by DNA variation. Thus we should conduct more detailed study on them in the future.DNAの変異分析については、Schizotetranychus属の多数の種についてミトコンドリアDNAのCOl領域の取り出しおよび塩基配列の決定を行い、国外ですでに決定されている同部位の配列情報と併せて、近隣結合法(NJ法)、最尤法等の複数の解析法を用いて系統解析した。その結果、現在の形態から行われた属の分類は、おおむね妥当であるが、例えばSchizotetranychus属は今後複数の属に分割されるべきだと考えられた。さらに、従来形態から提案されてきた属の系統関係については、計画段階で予想された通り、かなり変更される余地のあることが示唆された。